DE 40 24 096 C2 discloses a tool holder having a cutting tool for metal cutting, a minicutter bar in particular. A cutting insert is braced by a clamping leg resting against it on a flat clamping surface in a recess having cutting insert mounting surfaces of a lengthwise slotted forked holder shaft. In the disclosed solution, the clamping surface of the cutting insert is positioned in parallel with the axis of the holder shaft. The recess in the holder shaft has three cutting insert bearing surfaces, specifically, a bottom surface, a main cutting pressure support surface, and a back pressure support surface which include angles smaller than 90° both relative to each other and to a side surface and a frontal surface as the only open side surfaces.
In use of such tool holders, it is extremely important for cutting of work pieces with respect to the accuracy to be achieved in the machining process and especially also to the quality of the surfaces machined for it to be possible to mount the tool holder with its bearing surface absolutely rigid and to secure on the base holder by means of the fastening device. In other words, it must be made certain that force components acting between tool holder and base holder as shearing forces or forces of torque, ones which try to twist the tool holder on the base holder, will be introduced safely, that is, without impairing the secure seating, into the base holder by way of the bearing surface.
DE 195 17 365A1 discloses a tool holder for machining by turning, comprising a base recess as tool holder which may be mounted with its tool axis oriented perpendicular to the axis of rotation on a tool carrier as base holder. A cutter holder is mounted to be replaceable on the base recess, and a cutting plate is mounted on the cutter holder so as to be replaceable. The base recess itself has a bearing surface as bearing component extending transversely to the tool axis. The cutter holder has a mounting surface and is detachably mountable with this surface on the bearing surface on the base recess. The cutter holder is immobilized against all relative movements of the mounting surface relative to the bearing surface by fitting elements, the cutter holder having at least one cutting insert seat.
Since, in this disclosed solution, the bearing component is not configured to be planar, but rather is designed with a gear cutting geometry, and the mating teeth of tool holder and base holder have frontal surfaces which are diametrically opposite each other, despite the fitting elements referred to above, especially ones in the form of set screws, tilting processes occur. The tilting results in an adverse effect on the accuracy of machining with the indexable inserts seated in the tool holder, since the latter also are also tilted and accordingly displaced in their machining plane. In addition, because of the gear cutting geometries, the disclosed solution results in increased production costs, in particular if the respective toothing is to be produced as high-precision toothing.
U.S. Pat. No. 5,688,080 discloses a generic tool holder for cutting elements, indexable inserts in particular. The tool holder may be mounted on a base holder by a fastening device with three fastening screws and a bearing component operating in conjunction with this base holder. A bearing component extends in a planar configuration in the direction of the tool holder. The cutting forces generated by the cutting element are introduced into the base holder by the bearing component, such bearing component being of planar configuration and being divided by a recess which is introduced into planar components. Between the planar components, the recess forms a seat to receive a projecting fitting element of the base holder. The walls of the recess for the fitting element form support surfaces which define, in relation to each other, different planes which, planar in configuration, extend transversely to the bearing component to introduce into the fitting element of the base holder both the shearing forces resulting from the cutting force and the torsional forces. In the solution, as disclosed, the recess is, with the exception of an area of opening on an edge in the tool holder, delimited on all sides by three walls. The walls define planes, all of which extend perpendicularly to the plane of the planar components. In particular, with respect to such planar components during fastening of the tool holder to the base holder, over determinations occur which are offset by a wedge which may be adjusted by means of a twin screw inside a recess in the fitting element designed to be longitudinally displaceable. A twin screw effects compensation for play between tool holder and base holder. If the bearing play in question is offset in the disclosed solution by the wedge, changes in position in the active cutting area of the cutting element result, preventing high-precision machining from being carried out with the disclosed solution. This disclosed solution is not cost-effect in production in view of the great variety of components.